With the increasing number and functionality of implantable and wearable devices, the need increases for a reliable high-throughput and safe communication in and around the body. There are several technological options that can serve this need, and their suitability is judged by the properties of the communication channel (the human body) for the respective types of signals, the required size of the implementation and the achievable power-to-performance ratio. Further, for each type of signal there are safety limits for the signal amplitudes and duty cycles to prevent damage to the body for short and long term usage.
For medical applications, data communication methods exist that use the human body as transmission medium to communicate between devices worn on or near the human body. This for example enables the transmission of local sensor data obtained from a specific locality on the body of a patient to a central receiver device gathering these signals. Of course, many other applications of such communications methods are possible. Generally, such a communication network using the body as transmission medium may be referred to as a body area network (BAN). More recently, such methods has evolved into a new type of communication called body coupled communication (BCC) which allows data communication at very frequencies (HF) of up to 100 MHz.
In BCC type data communication, data signals are transmitted via the surface (i.e. skin) of the body. Enabling the use of HF carrier frequencies, this type of communication potentially obtains high data rates rendering this type of communication suitable for data communication between many kinds of wearable devices. However, in some situations (e.g. for medical purposes), it may also be desired to allow data communication with devices inside the body. Examples of this are data communication with a pacemaker to obtain operational feedback, or obtaining data from a wireless probe brought inside the body during a medical examination. Neither BCC type communication nor radio wave type communication are suitable for this task, as signals are only conveyed across the surface of the body (BCC) or in the air and cannot penetrate inside the body for communication purposes.
At present, there are no good solutions available that allow ‘body bound’ data communication between devices regardless of whether such devices are located on, near or inside the body. Due to the different nature of communication types suitable for reaching devices at various locations, different types of communication systems are to be relied upon in different situations.
The document US2004/202339 describes a technique of connecting a hearing aid to another device via the body of the person wearing the devices. It describes the use of ultrasound or wireless communications.